Modulation of macrophage polarization by titanium implant surfaces

Abstract

[eng] Macrophages are key players of the interaction between biomaterials and the immune system, presenting a great plasticity depending on the biomaterial’s physicochemical properties. Indeed, macrophages can either promote a tissue-inflammatory response (M1 macrophages) or a wound healing response (M2 macrophages), through their ability to switch polarization state in response to stimuli received from local changes in their microenvironment. In this study, an in vitro model of macrophage polarization was first set-up using the THP-1 cell line. THP-1 monocytes were differentiated on tissue culture plastic into macrophages (M0) by PMA incubation. PMA-differentiated macrophages (M0) were then co-stimulated with IFN-γ and lipopolysaccharide from Porphyromonas gingivalis for M1 polarization or stimulated with IL-4 for M2 polarization, and evaluated at three differentiation times (6h, 1 day, 7 days). Cytotoxicity, cell morphology, gene expression and surface markers on the different macrophage’s phenotypes obtained were evaluated. Afterwards, the effect of different Ti implant surfaces on macrophage polarization was investigated. First, in the set-up of the in vitro model, we were able to demonstrate resting macrophages M0 from monocytes (THP1 cells) by PMA induction, and then macrophage polarization into the M1 pro-inflammatory (TNFα and IL-6 mRNA levels), or the M2 anti-inflammatory phenotype (IL-10 mRNA levels). Second, we could observe differences on the polarization state for the different Ti implant surfaces tested, with lower proinflammatory state (IL-6 mRNA levels) for treated surfaces with the antioxidant quercitrin compared to control. Thus, in the present work we proved the applicability of macrophage polarization cell model for the evaluation of novel titanium implant surfaces.